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primusd
7
Mar 19, 2017
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Hey folks, I've seen a few comments on Head-Fi, but I wanted to do a quick check here with the MD community as I'm trying to get a sense of the real-world portability of the m9XX. With headphones generally in the 32-40 Ohm range, does the m9XX function adequately using only smartphone power (i.e. no separate battery pack)? Any variation between iDevices, Android or other smartphones (e.g. BB10, W10)?
Would also welcome any experience from Canadians ordering this and whether you got hit with any customs duty charges.
Thanks!
Mar 19, 2017
AlexVallejo
85
Mar 20, 2017
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You generally need to use an external power supply when connecting the m9xx to a mobile device via camera connection kit or on-the-go cable. iDevices cannot supply enough power to the m9xx through the camera connection kit so it requires the external 5V 2A supply. I think I have heard of some people using certain Android devices to power the m9xx without using an external power source, but I'm not sure which devices those were.
Mar 20, 2017
primusd
7
Mar 21, 2017
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Thanks Alex. I'd be interested to hear more experiences from others. I too have seen some references to Android (Samsung S4 & S7, + LG G4) but not iDevices.
Mar 21, 2017
JimmyNgai
1
Mar 24, 2017
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Is there any differences in performance between connecting m9xx to computers via USB ports and smartphones or tablets via OTG USB? I mean SNR, THD, jitter or anything that you can think of, given the condition that those devices can provide enough power and can send bit-perfect data to m9xx.
Mar 24, 2017
AlexVallejo
85
Mar 24, 2017
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As long as you use the included external power supply and USB cables, performance should be the same. Can't say what the performance will be if your mobile device can bus power the m9xx, we'd have to measure it. You generally need to use the external supply when connecting to mobile devices with CCK or OTG cables.
Mar 24, 2017
JimmyNgai
1
Mar 25, 2017
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Thanks for your reply. Do you mean that as long as I use the included power supply and USB cables, m9xx will sound the same no matter I connect it to a computer or a mobile device?
When using mobile devices without the external power supply, if m9xx did not OC (over current), could I safely assume that it still performed well? I am thinking what I need to do (in minimum) in order to get out most performance of m9xx. If I do not always need the external power supply, then m9xx is also a wonder gear that I can take to a shop to try out any headphones.
Mar 25, 2017
CalebRoberts
56
Mar 26, 2017
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Hi primusd, First quick answer - no. You probably shouldn't expect any smartphone to power any sort of USB-powered DAC, and much less a power amplifier. We made a quick survey maybe a year ago and I believe we found phones will produce a very minimal VBus supply for connected USB devices - 10 mA current at 5 V. m9xx needs >300mA at idle. Using m9xx with a mobile device requires that you first connect its 5V/2A jack to a USB power supply (such as the one supplied with m9xx) or a battery. When the m9xx boots from first connecting to this jack then it will present itself to the host device (smartphone) as a self-powered device. With this configuration the m9xx will draw no current from the smartphone and it will work. Just plugging in a bus-powered device to a smartphone probably results in the smartphone immediately removing power from the USB Vbus pin. It's not a matter of whether you can sneak past a maximum load specification as long as it still work. A proper USB device tells the host how much power is required. Then the host will accept and enumerate if it's not over the host's limit. Hosts are supposed to have circuitry to prevent a device from drawing too much current. Of course there are many types of mobile devices and there may be something that will enumerate a 500mA device and that much power. Your notebook computer will probably do it but you might find your battery drains quickly. But yes if you're operating successfully from any 5V supply, as long as the OC message doesn't appear then m9xx will deliver the expected audio performance.
Mar 26, 2017
AlexVallejo
85
Mar 27, 2017
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The supplied USB cable with the ferrite bead should help with maintaining performance across bus powered connections. You shouldn't have any problem using it without the external supply.
Mar 27, 2017
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